Painted Cube Questions Follow the Position of Each Small Cube

Duration: 7 min

This video lesson is available to enrolled students.

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Inside: a video lesson and guided study material.

Module outline

  1. Child Development and Pedagogy: विकास की अवधारणा / Concept of Development, विकास के मनोवैज्ञानिक सिद्धांत / Psychological Theories of Development, व्यक्तिगत भिन्नताएँ, व्यक्तित्व एवं जेंडर / Individual Differences, Personality and Gender, बुद्धि एवं सृजनात्मकता / Intelligence and Creativity, अधिगम एवं इसके सिद्धांत / Learning and Its Theories, बालक कैसे सोचते एवं सीखते हैं / How Children Think and Learn, संवेग, अभिप्रेरणा, मानसिक स्वास्थ्य एवं निर्देशन / Emotion, Motivation, Mental Health and Guidance, समावेशी शिक्षा / Inclusive Education, शिक्षण-अधिगम प्रक्रिया / Teaching-Learning Process, शिक्षण विधियाँ एवं रणनीतियाँ / Teaching Methods and Strategies, आकलन एवं मूल्यांकन / Assessment and Evaluation, पाठ योजना और शिक्षण कौशल / Lesson Planning and Teaching Skills, शिक्षण संसाधन और शैक्षिक प्रौद्योगिकी / Teaching Resources and Educational Technology, कक्षा प्रबंधन और सम्प्रेषण / Classroom Management and Communication, शिक्षक पहचान और व्यावसायिक विकास / Teacher Identity and Professional Development, शैक्षिक विचारक, उद्देश्य एवं राष्ट्रीय नीतियाँ / Educational Thinkers, Aims and National Policies, जीवन कौशल, मूल्य, शांति एवं पर्यावरण शिक्षा / Life Skills, Values, Peace and Environmental Education, सामाजिक विज्ञान शिक्षणशास्त्र / Social Science Pedagogy, सामाजिक एवं राजनीतिक जीवन / Social and Political Life, विज्ञान शिक्षण शास्त्र / Science Pedagogy
  2. Language I — Hindi: भाषा, लिपि और वर्ण-विचार, संधि, शब्द-स्रोत और शब्द-रचना, समास, शब्द-भेद: विकारी और अविकारी, लिंग, वचन, कारक, काल और वाच्य, वाक्य-विचार और शुद्ध लेखन, शब्द-भंडार, रस, छंद, अलंकार और शब्द-शक्ति, हिंदी साहित्य, अपठित बोध, हिंदी शिक्षणशास्त्र, शिक्षा में ICT / ICT in Education
  3. Language II — English: Sounds, Spelling and Word Formation, Parts of Speech, Nouns and Pronouns, Articles, Determiners and Adjectives, Verbs and Modals, Tenses and Subject–Verb Agreement, Adverbs, Prepositions and Conjunctions, Sentence Structure, Voice and Narration, Vocabulary, Sentence Correction and Writing Skills, Poetry and English Literature, Reading Comprehension, Pedagogy of English Language
  4. Language II — Urdu: رسم الخط، املا اور تلفظ, ذخیرۂ الفاظ, قواعد, محاورے اور ضرب الامثال, شعر و سخن, اردو ادب کی تاریخ, تفہیمِ عبارت, اردو کی تدریس
  5. Language II — Sanskrit: वर्णविचारः एवं संज्ञाप्रकरणम्, सन्धिप्रकरणम्, शब्दरूपाणि, धातुरूपाणि, कारकाणि एवं विभक्तयः, उपसर्गाः एवं अव्ययानि, प्रत्ययप्रकरणम्, समासप्रकरणम्, वाच्यप्रकरणम्, संख्याज्ञानम्, शब्दज्ञानम् एवं अनुवादः, अपठितावबोधनम्, संस्कृतसाहित्यम् एवं काव्यशास्त्रम्, संस्कृतशिक्षणशास्त्रम्
  6. Mathematics: संख्या पद्धति एवं स्थानीय मान / Number System & Place Value, मूलभूत संक्रियाएँ, सरलीकरण एवं पैटर्न / Basic Operations, Simplification & Patterns, गुणनखंड, विभाज्यता, म.स.प. एवं ल.स.प. / Factors, Divisibility, HCF & LCM, भिन्न एवं दशमलव / Fractions & Decimals, वर्ग, घन, घातांक एवं करणी / Squares, Cubes, Exponents & Surds, मापन: लंबाई, भार, धारिता, समय एवं मुद्रा / Measurement: Length, Mass, Capacity, Time & Money, बीजगणित / Algebra, अनुपात, समानुपात, औसत एवं आयु / Ratio, Proportion, Average & Ages, प्रतिशत, लाभ-हानि एवं ब्याज / Percentage, Profit–Loss & Interest, समय-कार्य एवं चाल-दूरी / Time & Work and Speed–Distance, रेखाएँ, कोण, आकृतियाँ एवं निर्देशांक / Lines, Angles, Shapes & Coordinates, त्रिभुज, चतुर्भुज, वृत्त एवं त्रिकोणमिति / Triangles, Quadrilaterals, Circles & Trigonometry, क्षेत्रमिति: परिमाप, क्षेत्रफल एवं आयतन / Mensuration: Perimeter, Area & Volume, आँकड़ा प्रबंधन, सांख्यिकी एवं प्रायिकता / Data Handling, Statistics & Probability, गणित शिक्षणशास्त्र / Mathematics Pedagogy, गणितीय संक्रियाएँ एवं अंकगणितीय तर्क / Mathematical Operations & Arithmetical Reasoning
  7. Environmental Studies: परिवार, मित्र और समुदाय / Family, Friends and Community, पौधे / Plants, जंतु / Animals, खेती और पशुपालन / Farming and Animal Husbandry, भोजन और पोषण / Food and Nutrition, शरीर और स्वास्थ्य / Body and Health, जल / Water, आवास / Shelter, यात्रा, परिवहन और संचार / Travel, Transport and Communication, मानचित्र, दिशाएँ और भारत / Maps, Directions and India, हम क्या बनाते और करते हैं / Things We Make and Do, पृथ्वी, आकाश और आपदाएँ / Earth, Sky and Disasters, पर्यावरण, पारिस्थितिकी और वन्यजीव / Environment, Ecology and Wildlife, प्राकृतिक संसाधन, प्रदूषण और जलवायु परिवर्तन / Natural Resources, Pollution and Climate Change, पर्यावरण अध्ययन का शिक्षणशास्त्र / Pedagogy of Environmental Studies, प्राचीन भारत का इतिहास / Ancient Indian History, पृथ्वी, ग्लोब एवं मानचित्र / Earth, Globe and Maps, भौतिक भूगोल / Physical Geography, प्राकृतिक वनस्पति, वन्य जीवन एवं विश्व के प्रदेश / Natural Vegetation, Wildlife and World Regions, भारत का भूगोल / Geography of India, संसाधन एवं विकास / Resources and Development, भारतीय संविधान / Indian Constitution, सरकार: केंद्र, राज्य एवं स्थानीय / Government: Union, State and Local, बल, दाब, कार्य एवं ऊर्जा / Force, Pressure, Work and Energy, ऊष्मा एवं ध्वनि / Heat and Sound, प्रकाश / Light, ब्रह्मांड एवं प्राकृतिक परिघटनाएँ / Universe and Natural Phenomena, पदार्थ एवं उसकी संरचना / Matter and Its Structure, धातु, अधातु एवं दैनिक उपयोग की सामग्री / Metals, Non-metals and Materials of Daily Use, सजीव जगत: वर्गीकरण, कोशिका एवं ऊतक / Living World: Classification, Cell and Tissues, मानव शरीर एवं अंग तंत्र / Human Body and Organ Systems, भोजन, पोषण एवं स्वास्थ्य / Food, Nutrition and Health, पर्यावरण एवं पारिस्थितिकी / Environment and Ecology, उत्तर प्रदेश सामान्य ज्ञान / Uttar Pradesh GK, पादपों में पोषण, परिवहन एवं जनन / Plants: Nutrition, Transport and Reproduction, खेल जगत / Sports, अंतरराष्ट्रीय संबंध एवं संगठन / International Relations & Organisations, प्रमुख नियुक्तियाँ एवं पदधारक / Key Appointments & Office Holders
  8. अतिरिक्त अभ्यास / Extra Practice (beyond syllabus): भारतीय अर्थव्यवस्था: आँकड़े एवं समसामयिकी / Indian Economy: Data & Current Affairs, भारतीय कला एवं संस्कृति / Indian Art & Culture, विज्ञान एवं प्रौद्योगिकी / Science & Technology, पर्यावरण एवं जलवायु समसामयिकी / Environment & Climate Affairs, रक्षा एवं सुरक्षा / Defence & Security, स्थिर सामान्य ज्ञान / Static General Knowledge, सरकारी योजनाएँ, शासन एवं आधारभूत संरचना / Government Schemes, Governance & Infrastructure, क्रम, बैठक व्यवस्था एवं पहेली / Ranking, Seating Arrangement & Puzzles, कैलेंडर एवं घड़ी / Calendar & Clock, पासा एवं घन / Dice & Cubes, मध्यकालीन भारत का इतिहास / Medieval Indian History, औपनिवेशिक भारत एवं समाज सुधार / Colonial India and Social Reform, भारतीय राष्ट्रीय आंदोलन एवं स्वतंत्र भारत / Indian National Movement and Independent India, प्रौद्योगिकी, मापन एवं गति / Technology, Measurement and Motion, रासायनिक अभिक्रियाएँ, अम्ल, क्षार एवं लवण / Chemical Reactions, Acids, Bases and Salts, अर्थशास्त्र एवं भारतीय अर्थव्यवस्था / Economics and Indian Economy, विद्युत एवं चुंबकत्व / Electricity and Magnetism, बिहार सामान्य ज्ञान / Bihar GK, राजस्थान सामान्य ज्ञान / Rajasthan GK, पाठ्यचर्या और विद्यालयी गतिविधियाँ / Curriculum and School Activities, कंप्यूटर हार्डवेयर एवं परिधीय उपकरण / Computer Hardware and Peripherals
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This lesson explains painted cube questions by linking each small cube's position to its number of painted faces. The instructor uses a table and 3D diagram to show that corner cubes have 3 painted faces, edge cubes (excluding corners) have 2, face-interior cubes have 1, and completely interior cubes have 0. Formulas are given: 8 corners; 12(n-2) edge cubes; 6(n-2)^2 face-interior cubes; and (n-2)^3 interior cubes. A useful result is derived: small cubes with at least two painted faces equal 8 + 12(n-2) = 12n - 16. The lesson then applies this to a word problem: an 18 cm cube painted on all faces is cut into 3 cm cubes. Since n = 18/3 = 6, the number of small cubes with exactly two painted faces is 12(6-2) = 48. The solution is verified by summing all categories: 8 + 48 + 96 + 64 = 216, which equals 6^3.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The video introduces painted cube questions with a table categorizing small cubes by position and number of painted faces. The instructor highlights the 'Painted faces' column, underlines 'On an edge, excluding corners', and circles the value 2 and formula 12(n - 2). A large cube diagram is annotated with red arrows pointing to edges and corners, visually connecting the table's abstract categories to specific locations on a 3D model. The full table is shown: corner (3 faces, 8), edge excluding corners (2 faces, 12(n-2)), inside a face excluding edges (1 face, 6(n-2)^2), and completely inside (0 faces, (n-2)^3).

  2. 2:00 – 5:00 02:00-05:00

    The instructor progressively highlights each row of the table with red circles and boxes, moving from corner cubes (3 faces) through edge cubes (2 faces, formula 12(n-2)) to face-interior cubes (1 face, formula 6(n-2)^2) and completely interior cubes (0 faces). A 'Useful result' is derived: small cubes with at least two painted faces equal 8 + 12(n-2) = 12n - 16. A verification step shows that all four formulas sum to n^3, confirming the partition is complete. The segment transitions to a new slide titled 'Small Cubes with Exactly Two Painted Faces', presenting a word problem: an 18 cm cube painted yellow on all faces is cut into smaller cubes of side 3 cm each.

  3. 5:00 – 7:04 05:00-07:04

    The instructor solves the word problem by first calculating n = 18/3 = 6, the number of small cubes along one edge. The formula for exactly two painted faces is applied: 12(n-2) = 12(6-2) = 48. A summary slide titled 'Two Painted Faces Means Edge Cubes' confirms the answer of 48. An independent verification sums all categories: 8 corners + 48 edge cubes + 96 face-interior cubes + 64 interior cubes = 216, which equals 6^3, confirming the solution is consistent with the total number of small cubes.

The core teaching progression moves from general classification to specific application. First, the instructor establishes a complete taxonomy of small cube positions within a larger divided cube, assigning each position a fixed number of painted faces and a counting formula. The key insight is that exactly two painted faces corresponds uniquely to edge cubes excluding corners, counted by 12(n-2). The 'at least two painted faces' result (12n - 16) combines corner and edge cubes. The worked example demonstrates the standard method: compute n from side lengths, identify the relevant position category, apply its formula, and verify by summing all categories to n^3. This verification step is a critical exam technique that catches arithmetic or categorization errors.

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